Betaines, sultaines, and amine oxides have been used in consumer products for many years. These high performance amphoteric or amphoteric-type compounds can be used alone or in combination with commonly used anionic surfactants to provide products with enhanced properties: reduced skin and eye irritation, reduced dryness, smoother skin feel, better hair conditioning, and the like. Their use in formulations enhance viscosity building, foam development, and cleansing performance. Generally, these materials, particularly the betaine and amine oxide surfactants, are available commerically as aqueous solutions in 30% concentrations of active ingredients (AI), by weight. In general, the maximum concentrations of surfactant obtainable in the finished raw materials are determined by the rheological properties of the surfactant systems. Below about 30% concentration, the surfactant systems are free flowing isotropic solutions. Above this concentration, liquid crystalline phases are formed which have undesirable Theological properties. Some of the phases have very high viscosity. Manipulation of the surfactants with these phases is very difficult. The handling of this type of system is, therefore, quite inconvenient. For this reason, surfactant compositions with higher concentrations are not commercially available at this time. Among the benefits of higher active concentration materials are: reduced cost of shipping; less storage space; purer, more uniform product; availability of super concentrated finished products; and a greater resistance to microbial degradation.
Therefore, there have been efforts directed to preparation of higher percent AI materials. Hamann, et al, U.S. Pat. No. 5,464,565 utilized the addition of lower alkyl molecular weight tertiary amino acids (betaine or betaine like) e.g., trimethylglycine, to the reaction mixture in the preparation of betaine surfactant from its corresponding amine base and the monochlorosodium acetate reactant. Additionally, Weitemeyer et al, U.S. Pat. No. 5,354,906, retained small amounts, approximately 1 to 3 wt %, of fatty acid in the final betaine mixture. These methods are only nominally effective. While they increased total solids to about 45 to 50 wt %, they raise the active ingredient level percent of Al to only 40 wt % while introducing unwanted extra impurities into any finished formulation. In an attempt to overcome the limitations of aqueous systems, Bade, et al, U.S. Pat. No. 4,832,781, describes preparing betaine in isopropyl alcohol and other lower molecular weight polar organic solvents followed by azeotropic distillation of water. While preparing concentrations up to about 70 wt. % AI, the removal of the solvent before or after concentration remains an undesirable necessity. All of these attempts were made to obtain a high concentration of surfactants in isotropic solution form. Sometimes the transformation of phases from intractable systems to ones having desirable Theological properties can be achieved by utilizing additives such as fatty alcohols, fatty acids, fatty esters, or blending with other surfactants and organic solvents. Messenger et al, U.S. Pat. No. 4,243,549 was able to obtain lamellar liquid crystalline phase with 60 to 70 wt % surfactant concentration by blending alkyl betaines with anionic surfactants.
Therefore, there still exists significant motivation for a workable, pourable, pumpable solution of amphoterics such as betaines and/or sultaines together with an amine oxide of a relatively high weight percent AI concentration.